title: Identification of novel Ras-cooperating oncogenes in Drosophila melanogaster: a RhoGEF/Rho-family/JNK pathway is a central driver of tumorigenesis.
abstract: We have shown previously that mutations in the apico-basal cell polarity regulators cooperate with oncogenic Ras (Ras(ACT)) to promote tumorigenesis in Drosophila melanogaster and mammalian cells. To identify novel genes that cooperate with Ras(ACT) in tumorigenesis, we carried out a genome-wide screen for genes that when overexpressed throughout the developing Drosophila eye enhance Ras(ACT)-driven hyperplasia. Ras(ACT)-cooperating genes identified were Rac1 Rho1, RhoGEF2, pbl, rib, and east, which encode cell morphology regulators. In a clonal setting, which reveals genes conferring a competitive advantage over wild-type cells, only Rac1, an activated allele of Rho1 (Rho1(ACT)), RhoGEF2, and pbl cooperated with Ras(ACT), resulting in reduced differentiation and large invasive tumors. Expression of RhoGEF2 or Rac1 with Ras(ACT) upregulated Jun kinase (JNK) activity, and JNK upregulation was essential for cooperation. However, in the whole-tissue system, upregulation of JNK alone was not sufficient for cooperation with Ras(ACT), while in the clonal setting, JNK upregulation was sufficient for Ras(ACT)-mediated tumorigenesis. JNK upregulation was also sufficient to confer invasive growth of Ras(V12)-expressing mammalian MCF10A breast epithelial cells. Consistent with this, HER2(+) human breast cancers (where human epidermal growth factor 2 is overexpressed and Ras signaling upregulated) show a significant correlation with a signature representing JNK pathway activation. Moreover, our genetic analysis in Drosophila revealed that Rho1 and Rac are important for the cooperation of RhoGEF2 or Pbl overexpression and of mutants in polarity regulators, Dlg and aPKC, with Ras(ACT) in the whole-tissue context. Collectively our analysis reveals the importance of the RhoGEF/Rho-family/JNK pathway in cooperative tumorigenesis with Ras(ACT).
authors.affiliation: Peter MacCallum Cancer Center, Melbourne, Victoria, Australia.
authors.forename: Anthony M
authors.initials: AM
authors.lastname: Brumby
authors.forename: Karen R
authors.initials: KR
authors.lastname: Goulding
authors.forename: Tanja
authors.initials: T
authors.lastname: Schlosser
authors.forename: Sherene
authors.initials: S
authors.lastname: Loi
authors.forename: Ryan
authors.initials: R
authors.lastname: Galea
authors.forename: Peytee
authors.initials: P
authors.lastname: Khoo
authors.forename: Jessica E
authors.initials: JE
authors.lastname: Bolden
authors.forename: Toshiro
authors.initials: T
authors.lastname: Aigaki
authors.forename: Patrick O
authors.initials: PO
authors.lastname: Humbert
authors.forename: Helena E
authors.initials: HE
authors.lastname: Richardson
mesh_terms: D000818:Animals; D002454:Cell Differentiation; D002460:Cell Line; D049109:Cell Proliferation; D048430:Cell Shape; D002470:Cell Survival; D002999:Clone Cells; D029721:Drosophila Proteins / Q000378:metabolism*; D004331:Drosophila melanogaster / Q000166:cytology / Q000201:enzymology* / Q000235:genetics; D005123:Eye / Q000166:cytology / Q000254:growth & development / Q000648:ultrastructure; D017344:Genes, Insect / Q000235:genetics; D011905:Genes, ras; D020662:Guanine Nucleotide Exchange Factors / Q000378:metabolism*; D006801:Humans; D048031:JNK Mitogen-Activated Protein Kinases / Q000378:metabolism*; D020935:MAP Kinase Signaling System; D011230:Precancerous Conditions / Q000201:enzymology* / Q000473:pathology; D011493:Protein Kinase C / Q000378:metabolism; D015203:Reproducibility of Results; D064067:Rho Guanine Nucleotide Exchange Factors; D015854:Up-Regulation / Q000235:genetics; D020741:rho GTP-Binding Proteins / Q000378:metabolism*
chemical_list: D029721:Drosophila Proteins; D020662:Guanine Nucleotide Exchange Factors; D064067:Rho Guanine Nucleotide Exchange Factors; C115015:PKC-3 protein; D011493:Protein Kinase C; D048031:JNK Mitogen-Activated Protein Kinases; D020741:rho GTP-Binding Proteins